It is known to provide a slider window assembly for an opening of a vehicle, such as a rear slider window assembly for a rear opening of a pickup truck. Conventional slider window assemblies for rear openings of trucks or the like typically include three or more panels, such as two fixed window panels and a slidable window panel. The slidable window panel is supported by rails and may be moved along the rails to open and close the window. Typically, the upper rail includes a resilient filler and is sized to be able to sufficiently receive the upper edge region of the slidable window panel to allow for a carrier at the lower edge region of the slidable window panel to be aligned with and dropped or lowered into the lower rail.